The Detection of Impact Damage to the Edges of CFRP Plates Using Extensional Ultrasonic Edge Waves

Abstract

Extensional edge waves propagate along the edges of plates, with low attenuation in the propagation direction and amplitude decreasing rapidly (within one or two wavelengths) in the direction perpendicular to the plate edge. This makes them an ideal candidate for inspecting the edges of plate-like structures. Here, finite-element models and experiments are used to investigate the propagation and scattering of extensional edge waves in composite plates and application to damage detection is demonstrated. Piezoceramic transducers attached to the edge of a 4-mm-thick carbon-fibre-reinforced polymer (CFRP) plate were used to excite 140-kHz edge waves and damage detection demonstrated using two experimental configurations: pitch-catch and two-transducer pulse-echo. Damage due to edge-on impacts of 5 J and 10 J were detected in both configurations. A mass-addition damage model was used to investigate the effect of damage location. Detection was specific to damage within 33 mm (1.5 wavelengths) of the plate edge with propagation unaffected by features beyond that distance. The time of arrival of reflected signals in pulse-echo mode was accurately predicted using the edge-wave group velocity indicating that this configuration can be used for locating damage on edges. The localisation of edge waves means that they can specifically detect damage at the edges of structures, and attenuation measurements indicate that their useful propagation distance is large (5.5 m).

Bending edge wave on a functionally graded fluid‐saturated porous magneto‐electro‐elastic plate

“…In recent years, Hughes et al [35,36] examined the features of fundamental edge wave mode numerically and experimentally. Some other experimental studies towards the detection of damages with the help of edge wave in thin elastic structures were done by Zhu et al [37,38], Wilde et al [39,40], and Chu and Courtney [41].…”

“…𝑁 1 = μ − χ𝑐 + M𝑐 − 𝑔(𝑛)𝜈 𝑠 ( μ𝑠 − χ𝑠 𝑐 ), 𝑁 2 = 1 − χ𝑐 − 𝑔(𝑛)𝜈 𝑠 (1 − χ𝑠 𝑐 ) and 𝑁 4 = 2 − μ − 𝑔(𝑛)𝜈 𝑠 (2 − μ𝑠 ) + 𝑔(𝑛) χ𝑠 𝑐 𝜈 𝑠 − χ𝑐 . Therefore, Equation (38) will exist if χ𝑐 ≠ 1 and 𝑁 2 ≠ 0.Case-IIThe proposed model can be decreased in the case of the bending edge wave on the isotropic plate together with the Winkler foundation model by considering the materials parameter used in the proposed model as follows: 𝑆 1 = 𝐸 1−𝜈 2 , 𝜙 𝑝 = 0, 𝐺 = 0, 𝑓 𝑥 2 𝑓 𝑥 3 (𝑛) = 2, 𝑁 1 = μ = 𝜈 (Poisson ratio), 𝑁 2 = 1, 𝑁 3 = 0, 𝑁 4 = (2 − μ), 𝜈 𝑠 = 0, 𝜏 𝑐 = 0, χ𝑐 = 0, M𝑐 = 0, 𝜎 0 = 0, 𝐷 = 2 𝜌 𝑠 = 𝜌 and neglecting the inertia term, the dispersion relation Equation(38) reduces to the form (with dimension), Variation of cut-off frequency for different foundation constant and grading index, (a) and (b) corresponding to Equations (40) and(41).…”